P Block : Structures and Properties
Group 15 = Dinitrogen #Dinitrogen is a colourless , odourless ,tasteless , chemically inert and non-toxic gas . #It has two isotopes with atomic masses 14 & 15 . #Freezing Point = 195.3 K ; Boiling Point = 239.6 K #At high temperatures , dinitrogen reacts directly with metals like Mg , Al , etc. and with non-metals , it forms covalent nitrides #Dinitrogen combines directly with Hydrogen at about 773 with hydrogen to form ammonia (Haber's Process) #It is slightly soluble in Water (23.2 cm3 per litre) Ammonia #it is colourless , pungent smelling gas and can be toxic at higher concentration . #Freezing Point = 198.4 K ; Boiling Point = 239.7 K #It is highly soluble in water and highly basic . #Ammonia can form intermolecular hydrogen bonding . #On heating , Ammonia liquefies and on heating , liquid Ammonia gives an intense cooling effect . Thus liquid ammonia is used as a refrigerant . Nitric Acid #Laboratory-grade Nitric Acid is 68 % by mass . #Pure Nitric Acid is a colourless liquid #Freezing Point = 231.4 K ; Boiling Point = 355.6 K #HNO3 is a planar molecule . #Conc. Nitric Acid is a strong oxidizing agent and attacks all metals except gold and platinum . Oxides of Nitrogen Phosphine #It is colourless gas with pungent odour , and is highly poisonous , sparingly soluble in water . #It does not react with acids or alkalis #It forms explosive mixture with oxygen or air . #It is a powerful reducing agent . #Phosphine gas when heated over 600 K , gives red phosphorous and hydrogen . Phosphorous Halides Phosphorous trichloride #It is colourless , oily liquid having specific gravity 1.6 . Phosphorous pentachloride #It is a yellowish white powder having sharp odour and sublimes 373 K . Oxyacids of Phosphorous # = Group 16 = Dioxygen #It is a colourless , odourless and tasteless gas . #Its solubility in water is to extnt of 30 cm3L-1 . The small amount of dioxygen dissolved in watr is responsible for aquatic life . #It can be absorbed in alkaline pyrogallol(Benzene with 3 -OH groups) #It can be liquified under pressure to a pale blue liquid (B.P. 90.2K) and on cooling it can be solidified into a light blue solid (M.P. 54.4 K) #It is heavier than air . #It is paramagnetic in Nature #Oxygen atom has three stable isotopes with atomic masses 16 , 17 ,18 . Ozone #Gaseous Ozone is blue , liquid ozone is blue black and solid ozone is violet black . #Ozone is derived from greek word "ozein" meaning to smell . It has a pungent odour . #In small concentrations it is harmless , but in higher concentration it is toxic resulting into nausea and headache . #As compared to Oxygen , Ozone is thermodynamically unstable . #Ozone acts as a powerful oxidizing agent next to Fluorine . #Ozone also behaves as a reducing agent when treated only with BaO2 and and H2O2 . #Estimation of Ozone : #Exhaust gases(NO) from supersonic jet aeroplanes deplete the ozone layer . #Freons in refrigerators also deplete the ozone layer . #Ozone forms Ozonoids with unsaturated hydrocarbons . Sulphur dioxide #It is a colourless , gas , acidic in nature and having pungent smell . It forms discrete molecules in solid state . #It is highly soluble in water . #It liquifies at room temperature under a pressure of 2 atm and boils at 263 K . #It acts as a strong reducing agent . #It also acts as an oxidizing agent . #It also acts as a ligand to form numerous coordination compounds . Sulphuric Acid #It is a colourless , dense , oily liquid . It has specific Gravity 1.84 at 298 K . #Freezing Point = 283 K ; Boiling Point = 611 K #Pure Sulphuric Acid has a strong affinity for water and it dissolves in it with evolution of lot of heat . #It is a strong acid with powerful affinity for water , less volatile and acts as an oxidizing agent . #It is highly viscous due to hydrogen bonding . #It ionizes in two steps . = Group 17 = Chlorine #It is greenish yelow gas with a characteristic pungent odour . #It is heavier than air . #It is poisonous gas . In smaller amounts it causes headache and irritation of nose , throat and lungs . #It can be liquefied easily into greenish yellow liquid which boils at 239 K . #It is soluble in water . It is called Chlorine Water . It smells like Cl2 . On cooling , the aqueous solution of chorine gives yellow crystal of Cl2.8H2O . Hydrochloric Acid #It is colourless gas with a pungent smell . #On liquefication , it gives a colourless liquid (BP=189K) which on freezing gives white crystalline solid (MP=159K) . It is highly soluble in water and ionizes giving a strongly acidic solution . #At ordinary concentration , HCl contains about 37% (12N) acid . Interhalogen Compounds #They are covalent in nature . #All these compounds are volatile . #They are diamagnetic in Nature . #They are more reactive than halogens . #Thy act as strong oxidizing agents . = Group 18